This invention relates to a shut-off valve arrangement for occluding the flow of a fluid through the bore of a cannula.
In this specification the term cannula is intended to include a catheter or any other conduit for introducing liquid into or draining fluid from the body of a patient.
Various valve arrangements for occluding the flow of a body fluid through a fluid flow or infusion instrument are well known. Most of the known valve arrangements generally fall into two classes: those which include few components and are so inexpensive and those which include several separately manufactured components which require to be assembled and which are consequently more expensive. Typical examples of the valve arrangements of the first type are those disclosed in U.S. Pat. Nos. 4,198,973 and 5,429,616 which pinch the fluid bore in a catheter or cannula closed by some finger operated mechanism and which again opens the passage when the finger pressure on the mechanism is released. Although these valve arrangements are relatively cheap compared to the valve arrangements of the second type they require hands-on operation while closing the fluid passage of the conduit to which they are connected so restricting free hand use of the person who is inserting or removing the catheter or cannula into or from the body of a patient.
It is the object of this invention to provide a simple single piece cannula valve arrangement which is simply closed for hands-off insertion into or removal from the body of a patient.
A cannula valve arrangement which is made from a suitably resilient polymedic material including a body having a substantially cylindrical cavity for receiving a medical apparatus hub and a sleeve having a bore, for receiving a cannula, which is open into the body cavity according to the invention is characterised in that a zone of the body wall which defines the cavity is convexly bulged from the body and has a wall thickness which is less than that of the remainder of the body to enable the bulged portion of the body to snap from its convex shape into a concave shape in the body cavity when pressed over-centre into the body to close the bore of the sleeve to the cavity until again pressed outwardly from the cavity.
The diameter of the catheter sleeve bore may be significantly less than the diameter of the portion of the body which defines the cylindrical cavity with the axis of the sleeve bore being parallel to and eccentrically displaced from the axis of the cylindrical cavity with a transition portion of the body between the cylindrical cavity portion and the sleeve defining the bulged zone of the body.
The mouth of the cannula sleeve bore in the cylindrical cavity conveniently defines a valve seat and the inner surface of the bulge zone of the body carries an inwardly projecting valve member which when the bulged portion of the body is pressed into the cylindrical cavity closes the sleeve bore. The junction between the bulged portion of the body and the sleeve is preferably made in the form of a plastic hinge which is linear and normal to the direction of the cylindrical cavity and the sleeve bore axes.
The valve arrangement preferably includes a cannula which is fixed to the body sleeve with its bore in alignment with the sleeve bore.
The valve arrangement may include a needle which is eccentrically located in a hub with the needle projecting from the cannula and the hub located in the cylindrical cavity of the body with its leading end clear of the valve member in the cavity.
The invention additionally extends to a needle for use with the valve arrangement of the invention.